title: Novel approach for the efficient use of a full-scale, 3-dimensional model for cervical posterior fixation: a technical case report.
abstract: METHODS
  Case report of a patient with atlantoaxial subluxation who underwent posterior cervical fixation.
  
  
  OBJECTIVE
  To describe a novel approach for the efficient use of a full-scale, 3-dimensional model for preoperative planning and surgery.
  
  
  BACKGROUND
  Instrumented fusion of the cervical spine with screws and rods is indicated for atlantoaxial subluxation. Fatal complications, such as vertebral artery and spinal cord injuries, may occur during screw insertion. Making appropriate connecting rods, after screw insertion, is often time consuming. Therefore, precise preoperative planning and careful intraoperative procedures are required.
  
  
  METHODS
  A 73-year-old male with atlantoaxial subluxation presented with progressive quadriplegia and gait disturbance. Surgery involving a C1 laminectomy and posterior cervical fixation was planned; and a 3D model, allowing visualization of the vertebral artery, was developed. Bilateral C1 and C4 lateral mass screws and C2 pars screws were experimentally inserted into the model. Rods with appropriate curvature were created to obtain rigid screw fixation, and were used during the surgery. Moreover, radiography and computed tomographic images of the instrumented model were analyzed to ensure the proper orientation of the screws.
  
  
  RESULTS
  During surgery, screw insertion was performed, under fluoroscopic guidance, and compared with the 3D model and its preoperative radiographs. According to the preoperative analysis of the model-computed tomographic images, the direction of the C1 lateral mass screws was changed laterally, and the lengths of the C2 pars screws were shortened to avoid complications. The sterile, prebent rods could be elegantly adapted to the screws without additional bending. The postoperative course was uneventful, and postoperative computed tomographic images showed proper screw positioning.
  
  
  CONCLUSIONS
  Three-dimensional models that allow (1) visualization of the vertebral artery, (2) evaluation of radiological images after screw insertion, and (3) the use of prebent rods during surgery contribute to the safety of the cervical posterior fixation.
  
  
  METHODS
  N/A.
authors.affiliation: From the Department of Neurosurgery, National Hospital Organization, Nagasaki Kawatana Medical Center, Higashisonogi-gun, Nagasaki, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Toyoda
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Urasaki
authors.forename: Yuzo
authors.initials: Y
authors.lastname: Yamakawa
mesh_terms: D000368:Aged; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000601:surgery; D001863:Bone Screws; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D004204:Joint Dislocations / Q000000981:diagnostic imaging / Q000601:surgery; D007796:Laminectomy / Q000379:methods*; D008297:Male; D008953:Models, Anatomic; D019637:Orthopedic Procedures / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome